1. Field of the Invention
This invention relates to glutaric anhydride polymers, imide polymers produced therefrom, and to processes for producing said polymers in an extruder.
2. Description of Prior Art
In my U.S. Pat. No. 4,246,374 of Jan. 20, 1981, I disclose polymers containing imide units of any desired degree of imidization without the use of added water or solvent, using an extruder and feeding polymers containing units derived from esters of acrylic or methacrylic acid.
Others, D. H. Grant et al, Polymer 1, 125 (1960), for example, disclose preparation of polyglutaric anhydride which is shown as being crosslinked and hence would be insoluble in dimethyl formamide ("DMF"), would not be processable, and would not be injection moldable.
J. C. Hwa et al, Am. Chem. Soc., Div. Polymer Chem., Preprints, 4, (1), 56 (1963), and A. Crawshaw and S. B. Butler, J. Am. Chem. Soc., 80, 5464 (1958), show uncrosslinked polyglutaric anhydride, not soluble in DMF, but rather is only swellable in DMF, and is not thermally stable; its onset of decomposition temperature is only 172.degree.-175.degree. C., and thus it would not be considered to be a processable product.
Graves, U.S. Pat. No. 2,146,209, discloses urea as a source of ammonia, and shows going directly from an acid to an imide, though not through the glutaric anhydride, and not in an extruder.
Schroeder, U.S. Pat. Nos. 3,244,679 and 3,284,425 show autoclave processes requiring lengthy heating time in the presence of inert dissolving or suspending solvent.
See also the prior art disclosed in my prior patent.
In spite of all of the prior work in this area, no one has been able to make a non-crosslinked anhydride polymer in a way which produced thermoformable, yet highly thermally stable and processable product. Furthermore, no one has been able to make the corresponding imide polymers free of methyl substitution and thermally stable.